The present invention relates in general to testing equipment for testing respirators or gas masks, and in particular to a new and useful perimetry device for measuring the field of view available to a person wearing the respirator or gas mask.
Devices for measuring an individual field of view, perimetry devices, are commercially available. One such device is shown in FIG. 1. This device, however, is meant strictly for testing field of view for a "bare faced" condition. Utilizing such device for an individual wearing a gas mask produces data of questionable accuracy and usefulness. It is very difficult to locate a subject's eye perpendicular with a 90.degree. point on a scale used in the apparatus of FIG. 1, when the subject is wearing a mask. Since the location of the subject's eye is crucial to obtaining a correct field of view reading, the locating process has very low accuracy for the conventional perimetry device. Even if eye location is attained it is virtually impossible to maintain the location for the duration of the test. Accordingly, the test is not readily reproducible. Several subjects were tested with the conventional device while they wore gas masks. Use of the conventional device was abandoned and the invention disclosed here was developed to provide more accurate and reproducible field of view testing.